Z-axis redundant display/multilayer display

ABSTRACT

A display system for presenting one or more planes of display information. The display system may include two or more display modules positioned in a spaced relationship in a stacked formation substantially along a Z-axis perpendicular to a display face of a display module. Each display module may be selectively activated to display a visual image or deactivated to a quiescent state. Further, when a display module is activated to display the viewed image, the viewed image can be viewed through a prior display module which is deactivated to a quiescent state.

TECHNICAL FIELD

The present invention primarily relates to the field of flat paneldisplays, particularly as implemented in systems where redundancy isdesired and/or required to insure continued display performance in theface of potential device failure. The present invention also applies tomulti-level security applications directly exploiting a displayexhibiting different classification levels of information displayed oneach screen (i.e., hardware separation of different security levels).The present invention also applies to three-dimensional (3D) imagingapplications where explicit Z-axis information is viewed directly viaoverlay replication without recourse to stereoscopic techniques, andeven to applications requiring “reality overlay” capability.

BACKGROUND INFORMATION

In various critical applications (mission-critical, flight-critical,space-critical) where a display system must exhibit a minimal level offault tolerance, flat panel displays and their CRT-based counterpartsachieve redundancy by way of adjacent tandem dual installation.Additional area on the surface of the console that houses the display isroutinely allocated for installation of backup displays andinstrumentation devices. In many applications (e.g., avionics, militaryvehicle deployments, etc.), such “real estate” is at a premium, leadingto a congested console with primary and secondary displays consumingprecious console surface area.

Redundancy has been traditionally achieved by allocating additional areaon the X-Y surface of the console. Extension in the X-Y direction ismandated due to one factor that all such display devices have in common:they are opaque structures. Because they are inherently opaquestructures, it is not possible to exploit the Z-axis in developingredundant display solutions. Thus, there is a need in the art for adisplay system that exploits the Z-axis in lieu of consuming more areaon the X-Y console surface, many significant advantages would accrue.

SUMMARY OF THE INVENTION

A first advantage of the present invention where the Z-axis is exploitedis that redundancy achieved by exploiting the Z-axis would directly freeup surface area on the display console. A second advantage is that thespace savings could readily be translated into larger, easier-to-readdisplays. A third advantage is that system wiring paths would be shorterand thus more reliable. A fourth advantage is an ergonomic one that isparticularly apparent in avionics. Since the backup display occupies theexact same location in the console, the user does not have to divert hisgaze to another location on the console to acquire importantinformation. All information is displayed in the same place under allconditions.

If a flat panel display were transparent, there would be little inprinciple to bar its being stacked in the Z-axis in pairs, or sets ofthree, etc. Flat panel displays conducive to such configuration mustexhibit four properties: they must be inherently transparent, they mustfail in the “off mode” to avoid undesirable overlay, they must berelatively thin along the Z-axis, and they must fulfill thesurvivability criteria for the particular environment calling forredundant implementation. (E.g., an environment requiring redundancy islikely to undergo extremes of temperature, militating against liquidcrystal display deployment at the outset. Some severe deployments mayrequire surviving an electromagnetic pulse.)

Among current display technologies, virtually none exhibit the requiredtransparency. Accordingly, little has been done to explore thepossibility of achieving redundancy using Z-axis disposition of theredundant display components. The problem has remained unsolved,although it is surely as urgent as it ever has been.

The present invention, called Z-Axis Redundant Display/MultilayerDisplay, achieves this elusive goal for displays that satisfy these fourcriteria. Among the display technologies that do indeed satisfy thesecriteria, therefore lending themselves to implementation of a Z-AxisRedundant Display/Multilayer Display, is the display disclosed in U.S.Pat. No. 5,319,491, which is hereby incorporated herein by reference inits entirety.

The display of U.S. Pat. No. 5,319,491 (hereinafter called a “TMOSDisplay”) is a known suitable candidate for systemic configuration intoa Z-Axis Redundant Display. It exhibits the requisite transparency, itfails in the off-mode without power, and it satisfies theperformance/environmental/survivability criteria associated withapplications demanding fault tolerance through device redundancy.

The present invention treats the TMOS Display as a modular element in alarger architectural construct. This construct, broadly conceived,involves the disposition of two or more TMOS Displays in spaced-apartrelation to each other, said relation keeping the planes of allconstituent TMOS Displays parallel. When TMOS Displays are used as thetarget module being replicated (as recommended), the interstitialspacing between them is nominally greater than the wavelength of thelowest frequency light traveling in each TMOS Display waveguide to avoidcrosstalk between displays occasioned by evanescent coupling. Theinterstitial gap cannot be filled with material bearing a highrefractive index, since TMOS Displays use the principle of FrustratedTotal Internal Reflection to generate images. The gap may be filled withair or material with a refractive index very near that exhibited by air(1.00-1.06). The present invention can incorporate displays other thanTMOS Displays that fulfill the criteria enunciated above; thelimitations inherent in these alternate candidates would directlyinfluence the geometry of the construct. From this point forward, theterm “module” will be taken to mean a TMOS Display or a generallyequivalent alternate candidate that satisfies the key viability criteriaherein tabulated. The term “construct” will refer to the systemiccomposition of two or more modules in spaced-apart relation to securethe benefits accruing to such composition.

The primary display in a construct may be the topmost/frontmost module,with the backup display(s) being one or more modules situatedunderneath/behind it. In one embodiment, only the primary displayoperates while the backup display(s) remain(s) quiescent. In the eventof failure of the primary display, the appropriate circuitry eitherdetects this fact or is apprised of it by operator action, shuts downpower to the primary display, activates the next backup display andreroutes video signals to the latter. If more than simple redundancyobtains, the failure of the secondary display would trigger theactivation of a tertiary display, etc., thus securing additionalredundancy as required.

The present invention is independent of any specific mounting technologyto hold the modules in the correct spaced relationship in the construct.It broadly covers all implementations of display redundancy in which thesalient features herein disclosed are in evidence. There may well belevels of sophistication in such mounting technologies that enable easeof module replacement within the construct. There may also be manyvariations in how to reroute information from the failed primary displayto a backup display (from one module to another). The present inventiondiscloses an overarching architecture from which such present and futuresophistications derive meaning and utility.

To achieve so-called “hardware separation” between data bearingdifferent security/classification levels, the same parallel moduledisposition can be applied. In this instance, the driver circuitry isnot geared to redundancy but rather to keeping displayed data bearing aspecific security clearance level on a specific module within the module“stack.” Users of such systems who lack the appropriate securityclearances will not receive information restricted to the correspondingmodule since that module will be deactivated or otherwise renderedquiescent. Only the modules in the stack for which the user hasclearance will be activated and permitted to display information.

Where a sufficiently large number of modules comprise a stack, it isfeasible to emulate explicit 3-dimensional objects by encoding the2-dimensional projected cross-section of these objects into therespective planes represented by the modules. The level of Z-axisgranularity under this emulation schema will be proportional to thenumber of modules comprising the stack and inversely proportional tointer-module spacing.

Applying redundancy to “reality overlay” applications (e.g.,helmet-mounted see-through displays) is also readily achieved byapplying the principles of the disclosed construct to the device undercontemplation. Since both modules are transparent, the reality overlaycriterion (the ability to view the real world through the display, whichis usually situated near the observer's eye) is maintained understandard operating mode with the primary display or in emergency backupmode with the secondary display within the construct displaying theviewable image.

In the case of a reality overlay display application, there is no opaquelayer comprising the final part of the construct, inasmuch as such alayer would be inconsistent with the “see through” criterion at theheart of such a system. However, such an opaque (black) layer may beused to provide a reference black background against which images aregenerated. There are two different ways to implement such an opaquebackground within the construct: (1) if the opaque background is static(fixed and unchanging in blackness), such as would be the case if itwere an extended planar sheet of carbon nanofoam, the layer must beplaced behind all the other modules; (2) if the opaque background isdynamic (capable of being switched between transparent and opaquemodes), this layer can be either situated as in (1) above, or can itselfbe replicated behind each module so that each layer of the construct hasits own dynamic black background.

The foregoing has outlined rather broadly the features and technicaladvantages of one or more embodiments of the present invention in orderthat the detailed description of the invention that follows may bebetter understood. Additional features and advantages of the inventionwill be described hereinafter which form the subject of the claims ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description is considered in conjunction with thefollowing drawings, in which:

FIG. 1 illustrates a single level of redundancy using a two-moduleconstruct in accordance with an embodiment of the present invention;

FIG. 2 illustrates a double level of redundancy using a three-moduleconstruct in accordance with an embodiment of the present invention;

FIG. 3 illustrates an arbitrary level of redundancy using an n-moduleconstruct in accordance with an embodiment of the present invention;

FIG. 4 illustrates a dual-module construct with a single static opaquelayer at the distal end of the module stack in accordance with anembodiment of the present invention;

FIG. 5 illustrates a dual-module construct with a dynamic opaque layersituated behind each individual module in the stack in accordance withan embodiment of the present invention;

FIG. 6 is a flowchart of a method for achieving redundancy for aconstruct comprising two modules in the stack with a static opaqueelement in accordance with an embodiment of the present invention;

FIG. 7 is a flowchart of a method for achieving redundancy for aconstruct comprising two modules in the stack with dynamic opaqueelements situated behind each module in accordance with an embodiment ofthe present invention;

FIG. 8 illustrates a “hardware-separated” multi-level security blockdiagram in accordance with an embodiment of the present invention;

FIG. 9 illustrates an explicit Z-axis quasi-three-dimensional constructof arbitrary granularity in accordance with an embodiment of the presentinvention;

FIG. 10 illustrates a “reality overlay” system exhibiting redundancy inharmony with the constructs disclosed in FIGS. 1, 2, and 3, inaccordance with an embodiment of the present invention;

FIG. 11 is a flowchart of a method for implementing hardware separationof data at different security classifications based on therepresentative constructive of FIG. 8 in accordance with an embodimentof the present invention;

FIG. 12 is a flowchart of a method for quasi-three-dimensional imagegeneration based on the construct of FIG. 9 in accordance with anembodiment of the present invention;

FIG. 13 illustrates a perspective view of a flat panel display inaccordance with an embodiment of the present invention;

FIG. 14A illustrates a side view of a pixel in a deactivated state inaccordance with an embodiment of the present invention;

FIG. 14B illustrates a side view of a pixel in an activated state inaccordance with an embodiment of the present invention; and

FIG. 15 is a flowchart of a method for displaying different classes ofinformation on different modules in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details. In other instances,well-known circuits and algorithms have been shown in block diagram formin order not to obscure the present invention in unnecessary detail. Forthe most part, details involving timing considerations and the like havebeen omitted inasmuch as such details are not necessary to obtain acomplete understanding of the present invention and are within theskills of persons of ordinary skill in the relevant art.

As stated in the Background Information section, a complement oftransparent displays disposed in a spaced-apart relation along theZ-axis (display stacking) can provide valuable system redundancycharacteristics in conjunction with improved human factors engineering(identical position for the primary and backup display for any givenpiece of instrumentation). As before, a transparent display, whetherbased on a TMOS display or an equivalent alternate technology bearingthe requisite attributes, shall be termed a module, while thecomposition of modules into a system shall be termed a construct. Ageneral principle of the present invention in one embodiment isillustrated in FIG. 1. The construct may be composed of a primary module100 and a secondary backup module 101, the primary planar surfaces ofwhich are maintained in a substantially parallel spaced apart relation102 by any arbitrarily chosen mounting mechanism (not shown). (Note, thepresent invention is not to be limited to such parallel constructions;it is also applicable to modules positioned at angles to each other.)The invention relates to the achievement of useful display redundancy,and therefore generalizes the means for mounting the displays in thecorrect geometric relations. Such mounting mechanisms can incorporateshock and vibration absorbing mechanisms, signal interconnects, etc. Theinvention can coexist with any such sophistications in mounting themodules; in fact, it directs the purpose for the mounting mechanisms tobe ultimately chosen for any given implementation of the presentinvention. The distance 102 may be selected to provide desiredviewability of the construct in both normal and backup display operatingmodes (i.e., when 100 is displaying the desired image, and when 100 hasfailed or has been disabled and 101 is displaying the desired image,which is viewed through the now-quiescent module 100). The distance 102may be zero or greater in dimension.

Each module 100, 101 may include a matrix of optical shutters commonlyreferred to as pixels or picture elements as illustrated in FIG. 13.FIG. 13 illustrates a module 100, 101 comprised of a light guidancesubstrate 1301 which may further comprise a flat panel matrix of pixels1302. Behind the light guidance substrate 1301 and in a parallelrelationship with substrate 1301 may be a transparent (e.g., glass,plastic, etc.) substrate 1303. It is noted that module 100, 101 maycomprise other elements than those illustrated, such as disclosed inU.S. Pat. No. 5,319,491, which is hereby incorporated herein byreference in its entirety. It is further noted that each modulediscussed herein may be structured as disclosed in FIG. 13.

Each pixel 1302, as illustrated in FIGS. 14A and 14B, may comprise aglass substrate 1303, light guidance substrate 1401, a transparentconductive ground plane 1402, a deformable elastomer layer 1403, and atransparent electrode 1404.

Pixel 1302 may further comprise a transparent element shown forconvenience of description as disk 1405 (but not limited to a diskshape), disposed on the top surface of electrode 1404, and formed ofhigh-refractive index material, preferably the same material ascomprises light guidance substrate 1401.

In this particular embodiment, it is necessary that the distance betweenlight guidance substrate 1401 and disk 1405 be controlled veryaccurately. In particular, it has been found that in the quiescentstate, the distance between light guidance substrate 1401 and disk 1405should be approximately 1.5 times the wavelength of the guided light,but in any event this distance must be maintained greater than onewavelength. Thus the relative thicknesses of ground plane 1402,deformable elastomer layer 1403, and electrode 1404 are adjustedaccordingly. In the active state, disk 1405 must be pulled bycapacitative action, as discussed below, to a distance of less than onewavelength from the top surface of light guidance substrate 1401.

In operation, pixel 1302 exploits an evanescent coupling effect, wherebyTIR (Total Internal Reflection) is violated at pixel 1302 by modifyingthe geometry of deformable elastomer layer 1403 such that, under thecapacitative attraction effect, a concavity 1406 results (which can beseen in FIG. 14B). This resulting concavity 1406 brings disk 1405 withinthe limit of the light guidance substrate's evanescent field (generallyextending outward from the light guidance substrate 1401 up to onewavelength in distance). The electromagnetic wave nature of light causesthe light to “jump” the intervening low-refractive-index cladding, i.e.,deformable elastomer layer 1403, across to the coupling disk 1405attached to the electrostatically-actuated dynamic concavity 1406, thusdefeating the guidance condition and TIR. Light ray 1407 (shown in FIG.14A) indicates the quiescent, light guiding state. Light ray 208 (shownin FIG. 14B) indicates the active state wherein light is coupled out oflight guidance substrate 1401.

The distance between electrode 1404 and ground plane 1402 may beextremely small, e.g., 1 micrometer, and occupied by deformable layer1403 such as a thin deposition of room temperature vulcanizing silicone.While the voltage is small, the electric field between the parallelplates of the capacitor (in effect, electrode 1404 and ground plane 1402form a parallel plate capacitor) is high enough to impose a deformingforce thereby deforming elastomer layer 1403 as illustrated in FIG. 14B.Light that is guided within guided substrate 1401 will strike thedeformation at an angle of incidence greater than the critical angle forthe refractive indices present and will couple light out of thesubstrate 1401 through electrode 1404 and disk 1405.

The electric field between the parallel plates of the capacitor may becontrolled by the charging and discharging of the capacitor whicheffectively causes the attraction between electrode 1404 and groundplane 1402. By charging the capacitor, the strength of the electrostaticforces between the plates increases thereby deforming elastomer layer1403 to couple light out of the substrate 1401 through electrode 1404and disk 1405 as illustrated in FIG. 14B. By discharging the capacitor,elastomer layer 1403 returns to its original geometric shape therebyceasing the coupling of light out of light guidance substrate 1401 asillustrated in FIG. 14A. Additional details regarding the functionalityof pixels 1302 is disclosed in U.S. Pat. No. 5,319,491, which is herebyincorporated herein by reference in its entirety.

Returning to FIG. 1, whereas FIG. 1 illustrates a construct exhibitingsimple redundancy (a single backup module), FIG. 2 illustrates anembodiment of the present invention of a construct with doubleredundancy (employing both a secondary and a tertiary module for backingup the primary module). The primary module 200 is in parallel spacedapart relation to the first backup module 201, which is in turn inparallel spaced apart relation to the second backup module 202. Thedistances between primary and secondary modules (203) and betweensecondary and tertiary modules (204) satisfy the criteria previouslydisclosed for FIG. 1, passim.

FIG. 3 generalizes the present invention to any arbitrary level ofsystem redundancy and fault tolerance in accordance with an embodimentof the present invention. The primary display 300 has additionaldisplays in spaced apart relation 302 to it in a concatenated stackingsequence, up through the final level of redundancy represented by thelast module in the stack, 301. The spacing 301 between each element ofthis construct satisfies the criteria established for such interstitialspacing in FIG. 1. Any module in the stack may be used as the primarydisplay. Moreover, more than one module may be active at the same time.

FIG. 4 illustrates the construct of FIG. 1 with the addition of a staticopaque (black) planar background in accordance with an embodiment of thepresent invention. Module 400 is in parallel spaced-apart relation 403to backup module 401, while the static opaque planar background 402 isitself in spaced-apart relation 404 to backup module 402. The planarbackground 402 is termed static because it is considered permanentlyopaque, and not capable of dynamic shifting between opaque andtransparent states. It provides a contrasting background for theconstruct as a whole, both for 400 when it is operational as well as for401 when it is activated and displaying the image encoded in the videosignal being fed to the construct.

FIG. 5 illustrates the construct of FIG. 1 with the addition of at leastone dynamic opaque (black) planar background in accordance with anembodiment of the present invention. The primary module 500 is inparallel spaced apart relation to the backup module 502, whereas both500 and 502 have associated opaque planar backgrounds (501 and 503respectively) in parallel spaced-apart relation to them, such that 501is situated between 500 and 502, while 503 is situated on the obverseside of 502 from 501. Opaque planar background 501 must be capable ofdynamically shifting from opaque to transparent mode, while 502 may beeither a static or dynamic opaque planar background. When 500 isoperational, 501 may be in opaque (black) mode. Should 500 fail or bedeactivated, element 501 then becomes transparent in order for backupmodule 502 to be viewed through the combination of 500 and 501, with 503being set to opaque if it is dynamic rather than static in nature.

FIG. 6 illustrates an embodiment of the present invention of analgorithm of a simple redundancy construct, such as in FIG. 1. Thealgorithm applies to instances where a static planar background, as inFIG. 4, is incorporated. Referring to FIG. 6, the algorithm 600 of asimple redundancy construct may determine if the primary display failurehas been detected in step 601. If the failure has not been detected,then a determination is made in step 602 as to whether the operatorinitiated a reversion to the backup display. If the operator has notinitiated a reversion to the backup display then, in step 603, a systemclock initiates periodic polling of the primary display failuredetection and operator commands. Subsequent to the system clockinitiating periodic polling of the primary display failure detection andoperator commands, a determination is made in step 601 as to whether theprimary display failure has been detected.

If the primary display failure has been detected, then, in step 604, theprimary display is deactivated to place the primary display in aquiescent, fully transparent state. Referring to step 603, if theoperator initiated a reversion to the backup display, then, step 604,the primary display is deactivated to place the primary display in aquiescent, fully transparent state.

In step 605, the secondary display is activated and the video signalsare routed to the secondary display instead of to the primary display.

Where dynamic planar backgrounds are implemented, the modified algorithmof FIG. 7 may be imposed. It should be understood that both algorithms(FIGS. 6 and 7) are readily extensible and thus can be modified byanyone knowledgeable in the art to handle higher degrees of systemredundancy for more elaborate constructs, such as those disclosed inFIG. 2 or FIG. 3.

Referring to FIG. 7, FIG. 7 illustrates an embodiment of the presentinvention of an algorithm 700 where dynamic planar backgrounds areimplemented. In step 701, a determination is made as to whether theprimary display failure has been detected. If the failure has not beendetected, then a determination is made in step 702 as to whether theoperator initiated a reversion to the backup display. If the operatorhas not initiated a reversion to the backup display then, in step 703, asystem clock initiates periodic polling of the primary display failuredetection and operator commands. Subsequent to the system clockinitiating periodic polling of the primary display failure detection andoperator commands, a determination is made in step 701 as to whether theprimary display failure has been detected.

If the primary display failure has been detected, then, in step 704, theprimary display is deactivated to place the primary display in aquiescent, fully transparent state. Referring to step 703, if theoperator initiated a reversion to the backup display, then, step 704,the primary display is deactivated to place the primary display in aquiescent, fully transparent state.

In step 705, the primary display's dynamic opaque back layer isdeactivated thereby making the primary display's dynamic opaque backlayer transparent. Further, in step 705, the secondary display's dynamicback layer is activated thereby making the secondary display's dynamicback layer opaque.

In step 706, secondary display is activated and the video signals arerouted to the secondary display instead of to the primary display.

FIG. 8 illustrates application of an embodiment of the present inventionto the situation where hardware separation of displayed information isrequired to achieve multi-level security. For illustrative purposes, onecan assume that module 800 is hardwired to display information deemed“unclassified,” while module 801 is hardwired to display informationdeemed “confidential” while module 802 is hardwired to displayinformation deemed “secret.” The information system of which thistriplexed construct is a part would determine by user password analysiswhich of the displays will be activated and which ones will not, thusproviding valuable hardware separation of security levels in the displayof sensitive information. The parallel spaced-apart relationships 803and 804 follow the general criteria for such interstitial distancesdisclosed earlier. A method for displaying different classes ofinformation on different modules is discussed below.

FIG. 15 is a flowchart of an embodiment of the present invention of amethod 1500 for displaying different classes of information on differentmodules in accordance with an embodiment of the present invention.

Referring to FIG. 15, in step 1501, a first module, e.g., module 800(FIG. 8), is hardwired to display unclassified information. In oneembodiment, the first module may be hardwired to display unclassifiedinformation only if the user enters a password designated to allow theuser to retrieve unclassified information.

In step 1502, a second module, e.g., module 801 (FIG. 8), is hardwiredto display classified information. In one embodiment, the second modulemay be hardwired to display classified information only if the userenters a password designated to allow the user to retrieve classifiedinformation. The password that allows the user to retrieve classifiedinformation may be different from the password that allows the user toretrieve unclassified information.

In step 1503, a third module, e.g., module 802 (FIG. 8), is hardwired todisplay secret information. In one embodiment, the third module may behardwired to display secret information only if the user enters apassword designated to allow the user to retrieve secret information.This password may be different from the passwords that allow the user toretrieve unclassified and classified information.

Referring to FIG. 9, FIG. 9 illustrates the possibility of using anarbitrarily complex construct composed of many modules (900, 901, andall modules between them represented in dotted-outline format) inaccordance with an embodiment of the present invention. Each of themodules is in parallel spaced-apart relation 902 with its neighboringcounterparts in the stack. The quality of the three-dimensional imaginesgenerated is proportional to the number of modules and inverselyproportional to the distance 902, which defines the construct's Z-axisgranularity. With properly encoded information, it is possible togenerate a quasi-three-dimensional image using this construct. Theexample suggested by FIG. 9 is of a solid cylinder with its central axisbeing perpendicular to the planar surfaces of the modules 900 through901 comprising the construct. Each module in the stack comprising theconstruct displays the line of intersection between the threedimensional object being displayed and the plane of the module. For thisreason, the modules between 900 and 901 are shown as displaying only theouter ring of the cylinder. Excessive directionality of optical outputpower would vitiate the desired effect of solid objects being displayedwithin the limits of the construct.

FIG. 10 illustrates a “reality overlay” display system that incorporatessimple (single level) redundancy in accordance with an embodiment of thepresent invention. During normal operation, the observer views the worldthrough both modules 1000 and 1001. Module 1000 is the primary display,which may or may not be displaying information to be overlaid on thereal-world image as seen through the module. Such displayed informationas would appear on 1000 can be advisory, or it can include targetingreticles, digitally enhanced images, etc. Should module 1000 fail or bedisengaged by the observer, module 1001, which is in parallel spacedapart relation 1002 to module 1000, will be activated, and the observerwill again view the real world through both 1000 and 1001, but theoverlaid information will be emitted from the surface of 1001 ratherthan 1000. By definition, reality overlay display applications do notincorporate any opaque components, such as might be found in otherdisplay applications herein.

FIG. 11 is an embodiment of the present invention of a flowchart of amethod 1100 for implementing multi-level security using hardwareseparation as explicated in the description of FIG. 8. The various terms(login, polling, etc.) are not to be construed in a restrictive sense,but broadly, in keeping with the general principles well-known to anyoneskilled in the art of systems security.

Referring to FIG. 11, in step 1101, a determination is made as towhether the login flag is set for the first security level. If the loginflag is not set for the first security level, then in step 1102, adetermination is made as to whether the login flag is set for the secondsecurity level. If the login flag is not set for the second securitylevel, then in step 1103, a determination is made as to whether thelogin flag is set for the third security level. If the login flag is notset for the third security level, then in step 1104, all secure displaysare deactivated and reverted to login mode. In step 1105, the userlogins to the system to set security flags that determine which displaysare active. Upon setting security flags that determine which displaysare active, a determination is made as to whether the login flag is setfor the first security level in step 1101.

If the login flag is set for the first security level, then in step1106, display 800 (FIG. 8), associated with a first level of securityclearance, is activated. In step 1109, the user logs out of the systemor other semaphore is activated that flags for deactivation. Uponlogging out of the system or activating a flag for deactivation, allsecure displays are deactivated and reverted to login mode in step 1104.

If the login flag is set for the second security level, then in step1107, display 801 (FIG. 8), associated with a second level of securityclearance, is activated. In step 1109, the user logs out of the systemor other semaphore is activated that flags for deactivation. Uponlogging out of the system or activating a flag for deactivation, allsecure displays are deactivated and reverted to login mode in step 1104.

If the login flag is set for the third security level, then in step1108, display 802 (FIG. 8), associated with a third level of securityclearance, is activated. In step 1109, the user logs out of the systemor other semaphore is activated that flags for deactivation. Uponlogging out of the system or activating a flag for deactivation, allsecure displays are deactivated and reverted to login mode in step 1104.

FIG. 12 is an embodiment of the present invention of a method 1200 forimplementing quasi-three-dimensional imaging using the multiplicity ofoverlaid displays suggested in FIG. 9. In order to keep projectedenergies proportional to the surface contours of the objects beingdisplayed within this system, only the surface of the object isgenerated. The intersection of this surface with the virtual planeformed by each of the elements between display 900 and 901 inclusive(viz, including 900 and 901 themselves) provides the encoding frameworkfor feeding the appropriate information to each element with theconstruct contemplated in FIG. 9.

Referring to FIG. 12, in step 1201, the insertion of the 3-D object'ssurface with the virtual plane of the display is determined for eachdisplay within the multiplicity disposed between 900 (FIG. 9) and 901(FIG. 9). In step 1202, a determination is made as to whether thecalculated intersection does exist and can be encoded.

If the calculated intersection does exist and can be encoded, then, instep 1203, the line of intersection between the 3-D solid object and thevirtual plane of the selected display is encoded and that image isgenerated on the display. In step 1204, a determination is made as towhether all the displays between 900 and 901 have been polled.

If, however, the calculated intersection does not exist and/or cannot beencoded, then in step 1204, a determination is made as to whether allthe displays between 900 and 901 have been polled.

If all the displays between 900 and 901 have not been polled, then instep 1201, the insertion of the 3-D object's surface with the virtualplane of the display is determined for each display within themultiplicity disposed between 900 and 901.

If, however, all the displays between 900 and 901 have been polled, thenin step 1205, a frame of image data containing the data describing the3-D objects is accepted. Upon accepting the frame of image data, theinsertion of the 3-D object's surface with the virtual plane of thedisplay is determined for each display within the multiplicity disposedbetween 900 and 901 in step 1201.

Although the system and method are described in connection with severalembodiments, it is not intended to be limited to the specific forms setforth herein, but on the contrary, it is intended to cover suchalternatives, modifications and equivalents, as can be reasonablyincluded within the spirit and scope of the invention as defined by theappended claims.

1. A display system comprising: a first visually transparent displaymodule; and a second display module positioned in a spaced relationshipto the first display module in a stacked formation substantially along aZ-axis perpendicular to a display face of the first display module;wherein each display module can be selectively activated to display avisual image or deactivated to a quiescent state, and wherein when thesecond display module is activated to display the viewed image, theviewed image can be viewed through the first display module.
 2. Thedisplay system of claim 1, further comprising a third display modulepositioned in spaced relationship to the second display module in astacked formation substantially along the Z-axis.
 3. The display systemof claim 1, wherein when the second display module is in an active statedisplaying the viewed image, the first display module is visuallytransparent in the quiescent state.
 4. The display system of claim 1,wherein a single display module is activated to display an image at apoint in time.
 5. The display system of claim 1, wherein more than onedisplay module is activated to display an image at a point in time. 6.The display system of claim 1, further comprising a static opaque layerpositioned behind the second display module distal from the firstdisplay module in the Z-axis, wherein the second display module isvisually transparent.
 7. The display system of claim 1, furthercomprising a dynamic opaque layer positioned behind the second displaymodule distal from the first display module in the Z-axis, wherein thedynamic opaque layer can be activated to an opaque visual state anddeactivated to a transparent visual state.
 8. The display system ofclaim 1, further comprising an opaque layer positioned behind the seconddisplay module distal from the first display module in the Z-axis, and adynamic opaque layer positioned between the first and second displaymodules wherein the dynamic opaque layer can be activated to a visuallyopaque visual state and deactivated to a visually transparent state. 9.The display system of claim 1, wherein the first and second displaymodules are substantially parallel to each other along their X and Yaxes.
 10. The display system of claim 1, wherein the first and seconddisplay modules are not parallel to each other along their X and Y axes,but are aligned so that a viewed image displayed by the second displaymodule is viewable through the first display module.
 11. A method ofoperating a display system comprising the steps of: providing a firstvisually transparent display module, wherein the first visuallytransparent display module can be activated to display an image anddeactivated to a quiescent state; providing a second display modulepositioned in a spaced relationship to the first display module in astacked formation substantially along a Z-axis perpendicular to adisplay face of the first display module, wherein the second displaymodule can be selectively activated to display the image and deactivatedto a quiescent state; and activating a display module to display thevisual image, wherein when the second display module is activated todisplay the viewed image, the viewed image can be viewed through thefirst display module.
 12. The method of claim 11, further providing athird display module positioned in spaced relationship to the seconddisplay module in a stacked formation substantially along the Z-axis,wherein the third display module can be selectively activated to displaythe image and deactivated to a quiescent state, wherein when the thirddisplay module is activated to display the viewed image, the viewedimage can be viewed through the first and the second display modules.13. The method of claim 11, further comprising the step of activating asingle display module to display the image at a point in time, whereinwhen the second display is activated to display the image the firstdisplay module is visually transparent in the quiescent state.
 14. Themethod of claim 11, further comprising the step of activating more thanone display module to display the image.
 15. The method of claim 11,further providing a static opaque layer positioned behind the seconddisplay module distal from the first display module in the Z-axis,wherein the second display module is visually transparent.
 16. Themethod of claim 11, further providing a dynamic opaque layer positionedbehind the second display module distal from the first display module inthe Z-axis, wherein the dynamic opaque layer can be activated to anopaque visual state and deactivated to a transparent visual state. 17.The method of claim 16, further comprising the step of activating thedynamic opaque layer to an opaque visual state.
 18. The method of claim16, further comprising the step of deactivating the dynamic opaque layerto a transparent visual state.
 19. The method of claim 11, furtherproviding an opaque layer positioned behind the second display moduledistal from the first display module in the Z-axis, and a dynamic opaquelayer positioned between the first and second display modules, whereinthe dynamic opaque layer can be activated to a visually opaque visualstate and deactivated to a visually transparent state.
 20. The method ofclaim 19, further comprising the steps of: activating the first displaymodule to display the image; and activating the dynamic opaque layer toa opaque visual state.
 21. The method of claim 19, further comprisingthe steps of: activating the first display module to display the image;and deactivating the dynamic opaque layer to a visually transparentstate.
 22. The method of claim 19, further comprising the step of:activating the second display module to display the image, wherein thefirst display module is visually transparent in the quiescent state andthe dynamic opaque layer is in the deactivated visually transparentstate.
 23. The method of claim 19, wherein the opaque layer positionedbehind the second display module is a dynamic opaque layer, wherein thedynamic opaque layer can be activated to a visually opaque visual stateand deactivated to a visually transparent state.
 24. The method of claim12, further providing a dynamic opaque layer positioned behind the thirddisplay module distal from the first display module in the Z-axis,wherein the dynamic opaque layer can be activated to an opaque visualstate and deactivated to a transparent visual state.
 25. The method ofclaim 12, further providing an opaque layer positioned behind the thirddisplay module distal from the first display module in the Z-axis, and adynamic opaque layer positioned between the first and second displaymodules, wherein the dynamic opaque layer can be activated to a visuallyopaque visual state and deactivated to a visually transparent state. 26.A display system comprising: a first visually transparent display modulehaving a display face; and a second display module having a displayface; wherein the display modules are positioned in a stacked formationsubstantially along a Z-axis perpendicular to a display face of thefirst display module, and wherein the display module faces are notaligned in the same in the X-Y plane; wherein each display module can beselectively activated to display a visual image or deactivated to aquiescent state, and wherein when the second display module is activatedto display the viewed image, the viewed image can be viewed through thefirst display module.
 27. The display system of claim 26, furthercomprising a third display module having a display face, the thirddisplay module positioned in spaced relationship to the second displaymodule in a stacked formation substantially along the Z-axis and whereinthe display module faces are not aligned in the same X-Y plane.
 28. Thedisplay system of claim 26, wherein the display module faces aresubstantially parallel to each other along their X and Y axis.
 29. Thedisplay system of claim 26, wherein the display module faces are notparallel to each other along their X and Y axes, but are aligned so thata viewed image displayed by the second display module is viewablethrough the first display module.
 30. The display system of claim 26,further comprising a dynamic opaque layer positioned behind the seconddisplay module distal from the first display module in the Z-axis,wherein the dynamic opaque layer can be activated to an opaque visualstate and deactivated to a transparent visual state.
 31. The displaysystem of claim 26, further comprising an opaque layer positioned behindthe second display module distal from the first display module in theZ-axis, and a dynamic opaque layer positioned between the first andsecond display modules wherein the dynamic opaque layer can be activatedto a visually opaque visual state and deactivated to a visuallytransparent state.
 32. The display system of claim 27, furthercomprising a dynamic opaque layer positioned behind the third displaymodule distal from the first display module in the Z-axis, wherein thedynamic opaque layer can be activated to an opaque visual state anddeactivated to a transparent visual state.
 33. The display system ofclaim 27, further comprising an opaque layer positioned behind the thirddisplay module distal from the first display module in the Z-axis, and adynamic opaque layer positioned between the first and second displaymodules, wherein the dynamic opaque layer can be activated to a visuallyopaque visual state and deactivated to a visually transparent state. 34.A display system comprising: a plurality of display modules positionedin a stacked formation substantially along a Z-axis, wherein each ofsaid plurality of display modules is positioned in a spaced-apartrelation with respect to one another; and a three-dimensional imagedisplayed in said plurality of display modules, wherein each of saidplurality of display modules displays a line of intersection betweensaid three-dimensional image and a plane of its display module.
 35. Adisplay system comprising: a first display module configured to displaya first type of information; and a second display module positioned in aspaced apart relation to said first display module, wherein said seconddisplay module is configured to display a second type of information;wherein said first type of information is displayed upon receipt of afirst password, wherein said second type of information is displayedupon receipt of a second password.